Standards such as 10GBASE-T, 40 GbE, and 100 GbE require communication links to function at multi-gigabits-per-second (Gb/s) data rates. As the data rate increases, the communication channel, such as coaxial or optical fiber cables, begin to impact the information quality. For example, inter-symbol interference (ISI) introduced by the channel must be corrected through equalization and/or forward error correction (FEC).
Digital circuit solutions for receivers have become more attractive for equalization and error correction due to the ease of abstraction in the design of digital signal processing (DSP). In order to implement digital signal processing on an analog wireline communication system, these digital solutions include an analog-to-digital converter (ADC). The ADC takes samples of the received analog signal and uses the samples to produce a digital signal, which can then be processed by the digital signal processing.
Receivers utilizing an ADC can introduce several additional disadvantages, however. Compared to analog or mixed-signal receivers, ADC-based receivers generally consume more power. ADC-based receivers are thus often reserved for applications where the signal degradation merits the additional cost, and often only used for medium reach communication channels (MR, 20 dB+ loss at one-half of the communication symbol rate) and long reach communication channels (LR, 30 dB+ loss) applications.